Preheat oven to 180 C / Gas 4. Grease and line a 20cm cake tin with baking parchment.
Into a mixing bowl, sift together the flour and cocoa powder. In a separate bowl, beat eggs then add to the flour and cocoa. Add the vanilla extract and sugar and beat well with an electric handheld mixer until smooth and well integrated. Let stand for 3 minutes. Transfer to the prepared cake tin.
Bake in the preheated oven for 40 minutes or until a skewer inserted into the centre comes out clean. Remove the cake from the oven and let cool for 5 minutes in the tin. Turn out onto a rack and allow to cool completely before decorating as desired.